Plans to give newly-qualified teachers up to five years to complete induction have been rejected by the General Teaching Council for Wales.
Instead, it says new entrants should be given a maximum of three years in which to meet the standards required to continue teaching in state schools.
The Assembly government has been consulting on whether to increase the current four-term limit on how long NQTs can carry out casual supply work before having to find a post that counts towards induction.
Wales has more newly-qualified primary teachers than posts available, and TES Cymru has reported on NQTs who have struggled to find even occasional work.
Proposed changes to the regulations would allow NQTs to work for up to five years on supply, and then apply for further extensions. The Assembly government says it expects most NQTs would complete induction within five years, and that it remains committed to the process as a foundation for future professional development.
The GTCW has reiterated its call for the Assembly to follow the Scottish model, where every NQT is guaranteed a one-year induction post after training.
Hayden Llewellyn, registrar of the GTCW, said: "The council would not want to see a situation where NQTs who are unable to secure permanent employment are lost to the profession, as a consequence of being unable to complete their induction period."
He said the council was concerned about the proposed five-year time limit, and instead had suggested three years as "a middle ground". He added: "The response suggests that a balance needs to be struck in respect of the amount of time an NQT may undertake supply work before completing statutory induction.
"This is important if the induction year is to have significance, professional standards maintained, and the benefits of the year-long support and mentoring received are to be meaningful."
Gethin Lewis, secretary of the National Union of Teachers Cymru, said both the GTCW and Assembly government should "get back to basics".
"Extending the period is not the answer. If concessions are made now, then nothing will be done to find a solution for more induction posts for NQTs," he said.
Anna Brychan, director of the National Association of Head Teachers Cymru, said: "We have supported moves to make induction more flexible. But we also think a guaranteed induction post should be taken seriously.
"A huge number of teachers will retire over the next few years. We don't want to have lost enthusiastic new talent in the meantime."
Dr Carl Peters, a spokesman for the Universities Council for the Education of Teachers in Wales, said there was broad support for the Scottish model.
But he added: "There are some aspects that concern us, including the permeability of the border for trainees from outside Scotland trying to find work in Scotland.
"We would work with the GTCW and unions to secure the best deal for students trained in Wales. But we would also wish to retain transfer opportunities between Wales and England."